As modern information technology advances, various types of displays have been widely used in screens for consumer electronic products such as mobile phones, notebook computers, digital cameras, and personal digital assistants (PDAs). Among these displays, liquid crystal displays (LCD) and organic electroluminescence displays (OELD) are the prevailing products in the market due to their advantages of being light-weight, compact, and low in power-consumption. The manufacturing process for both LCD and OELD includes forming semiconductor devices arranged in array on a substrate and the semiconductor devices include thin film transistors (TFTs).
In the conventional TFT array substrates, an amorphous silicon (α-Si) TFT or a low temperature polysilicon TFT is usually adopted as a switching device of each of a plurality of sub-pixels. In recent studies, oxide semiconductor TFTs have higher mobility comparing to α-Si TFTs and have better threshold voltage uniformity (Vth) comparing to low temperature TFTs. Thus, oxide semiconductor TFTs have the potential of becoming the key element in flat displays of the next generation.
If active layers of the TFTs are influenced by subsequent processes to occur electric shifting, the electric reliability of the TFTs is decreased, especially, the oxide semiconductor TFTs are acuter in this issue. Therefore, how to improve the stability of the active layers in TFTs is important in recent researches.